The field of metering pumps is selected in order to illustrate a nonexclusive area of application of the invention. It is known that, in a metering pump with mechanical control, control of the stroke of the piston or membrane, which provides aspiration and lifting of the fluid and thus control of the pump capacity, depends on the value of eccentricity of a rotary crank which gives rise to alternating movement of a connecting rod which is connected to the piston or membrane. Control of this value is provided by displacement of a movable device, for example, the screw of a screw-nut system, which is maneuvered by means of a rotary knob which is accessible from outside the pump housing and is connected to the stationary nut in translation relative to the housing. In some pumps, the cylinder is controlled by controlling the position of a stop which impedes the aspiration cam of a movable device which is connected to the membrane or piston. This control can be obtained by turning a rotary knob which is accessible from outside the housing. In these devices, there are also locking units for locking the movable assembly in a state which corresponds to the obtained control. In fact, the vibration caused by operation of the pump can give rise to loss of adjustment of the position of the movable assembly and thus give rise to loss of adjustment of the capacity value.
An object of the invention is to provide a device for simple locking of a control knob, in particular, of a system for controlling the capacity of a pump, and in particular, of a metering pump.
Thus, for this purpose, the object of the invention is to provide a device for locking the angular position of a control knob of a movable device which is mounted rotatably at the end of a substantially cylindrical support. The knob comprises a lateral face which is parallel to the axis of the cylindrical support. The locking device comprises a ring which is mounted so that it can slide along the support between a first position removed from the knob and a second position close to the knob. The ring is prevented from rotating relative to the support, at least in this second position. The lateral face comprises bosses which are arranged so that, in its second position, corresponding bosses of the ring engage with bosses of the lateral face of the knob for each of the positions of a plurality of specific angular positions of the knob.
In the locked position, the ring prevents loss of adjustment of the device, whereas, in the released position, it allows control to be carried out freely. Translational displacement of the ring between the two positions provides fast and simple locking and unlocking of the knob.
In practice, the bosses consist of serrations, applied to the lateral face of the knob which is cylindrical, and of corresponding serrations applied to the ring. The serrations are engaged axially with one another in the second position of the ring for the plurality of angular positions of the knob.
In addition, between the support and the ring, the device comprises means for locking the ring relative to the support in the second position of the ring.
This locking of the ring ensures that the knob remains locked. The ring is thus prevented from being displaced by the effect of vibration or impact, or by the effect of gravity, if the arrangement of the device is such that the locked position is at a high position of the ring and the released position is at a low position, so that the gravity would tend to unlock the knob.